Support for roof tubes of a fluid heater



Jan. 31, 1967 SUPPORT Filed. July 27, 1965 K. S. SVENDSEN FOR ROOF TUBES OF A FLUID HEATER 2 Sheets-Sheet 1 FIG. 2

FIG.

INVENTOR. KONRAD S SVENDSEN BY r/(W AGENT Jan. 31, 1967 K. s. SVENDSEN SUPPORT FOR ROOF TUBES OF A FLUID HEATER Filed July 27, 1965 2 Sheets-Sheet 2 l NVEN'TOK KONRAD S SVENDSEN BY 51% KW Jud-N AGENT United States Fatent G 3,301,226 SUPPORT FOR ROOFTUBES OF A FLUID HEATER Konrad S. Sveudsen, Bloomfield, Conn., assignorto Combustion Engineering, Inc., Windsor, Conn., a corporation of Delaware Filed July 27, 1965, Ser. No. 475,202 Claims. (Cl. 122-510),

This invention relates to tube supports and in particular to an apparatus for supporting generally horizontal roof tubes of a fluid heater such as a steam generator.

Fluid heaters such as steam generators which are fired with a fossil fuel have gas passages for conveying the combustion products away from the combustion zone. These passages in most of the large units have walls lined with water or steam cooled tubes to avoid problems that occur with the use of high temperature refractory and to provide additional heat absorbing surface. These gas passages also have tubes lining the roof of the passages.

These tubes which run horizontally across the roof must be supported at intervals to prevent excessive sagging into the passage. Also since the steam generator may be operating with pressure in the furnace and, if not, must at least be designed for occasional furnace puffs, the tubes must be bucked to prevent movement in the upward direction.

To avoid leakage through the roof either inwardly or outwardly a gas-tight seal must be provided. This is generally accomplished by locating a skin casing on the outside of the roof tubes. This skin casing is a thin metallic plate which is formed at its edges to incorporate flexibility thereby absorbing differential expansion between the heavy framing when the skin casing expands to a temperature approximating that of the tubes.

The heavy steel framing for the steam generator .expands at varying degrees depending on the temperature of the particular member. At the same time the tubes expand according to their own temperature which is a function of both the temperature of the fluid passing through the tube and the temperatureof the gases to which they are exposed. While the tubes are supported from this steel framing, they must be supported in such a way that the differential expansion is permitted. In many fluid heaters, particularly supercritical steam generators or separately fired superheaters, considerable temperature difference can occur bet-ween the various tubes in the roof due to the different temperatures of the fluids passing through the various tubes. In such a situation these tubes must be either securely welded together so that the stresses are locked in the tubes or permitted to expand with respect to one another. When this temperature difference is quite high, the solution of welding these tubes together is untenable because of the high stresses developed and accordingly the only practical solution is to permit the tubes to expand with respect to one another.

This solution has been met in the past with various methods of supporting these tubes which have involved supports which slide but which have proven relatively expensive in their application as compared to my invention. Here a relatively rigid support member is located above the roof tubes extending in a direction transverse to the tubes. This support member in conjunction with the skin casing forms a gas-tight seal. Bars running parallel to the roof tubes are supported from this support member and an inverted U-lug is welded on the roof tubes transverse to the run of the tubes with one leg of the U on either side of the tube center line. The bars pass through the U-lugs in sliding contact with the top of the U-lug thereby supporting the weight of the tubes. The tubes are 3,391,226 Patented Jan. 31, 1967 held down by either the skin casing or the support member.

, It is an object of my invention to provide an inexpensive sildable support for the roof tubes of a fluid heater. i

It is a further object to provide an apparatus which incorporates the gas sealing means with the structural support means for the tube supports. 7

Other and further objects of the invention will become apparent to those skilled in the art as the description proceeds.

With the aforementioned objects in view, the invention comprises an arrangement, construction and combination of the elements of the inventive organization in such a manner as to attain the results desired, as hereinafter more particularly set forth in the following detailed description of illustrative embodiments. These embodiments are shown by the accompanying drawings wherein:

FIGURE 1 is a sectional side elevation through a support system wherein an inverted channel is used as a support member;

FIGURE 2 is a sectional elevation through 2-2 of FIGURE 1;

FIGURE 3 is a sectional elevation of a roof support employed in conjunction with a support for superheater elements; and

FIGURE 4 is a sectional plan view taken through section 4-4 of FIGURE 3.

The steam generator has on the roof of the gas passageway .a plurality of roof tubes 2 which are generally horizontal and are parallel throughout the relevant portion of their length. These tubes must be supported to avoid sagging into the passage-way and also bucked from the top to prevent the tubes from lifting upwardly in the event of pressure within the passageway. The steam generator structure generally includes support steel which passes a distance about 12 to 18 feet over the roof of the furnace. The tubing is essentially supported from this building steel.

Long support rods 3 formed of 2 /2 inch standard pipe are fastened to the support steel. To the bottom of these rods an inverted channel 4 is welded with this channel being so located that its axis is transverse to the run of the furnace passageway roof tubes 2.

From the location where the channel 4 crosses over the 2 /2 inch O.D. roof tubes 2, a U-shaped support lug 5 is welded to the roof tube. This U-shaped lug is formed of a 7 inch plate inch wide and is bent so that its width is 1 /2 inch over-all while depth from the upper side of the roof tube 2 to the lower side of the upper surface of the lug is 1 inch. This lug is welded so that the legs are on either side of the tube center line. inch by inch bars 7 are welded to the lower edge of the inverted channel 4 after being placed so that they pass through the lug 5. The lug 5 then rests in sliding contact with the bar 7 with the passageway roof tube 2 being the tubes so that it tends to adopt the temperature of the tubes. End flanges 9 of the skin casing are bent upwardly at a sharp angle and welded to the inverted channel 4. A gas-tight seal is thus formed by this skin casing in conjunction with the inverted channel 4. A refractory insulation 10 is placed on top of the tubes underneath the skin casing with this refractory being applied 3 so that it does not extend above the upper surface of the tubes. timate contact with the tube 2 while preventing excessive access to the skincasing by the hot gases flowing through the passageway below.

Differential expansion during operation occurs not only between the different roof tubes 2 but between the roof tubes 2 and the inverted channel 4. Since the channel 4 is closely associated with the hot gases and the hot roof tubes 2, this channel also achieves a reasonably hightemperature level while the building steel from which" the Wall arrangement is supported will generally remain at ambient temperatures. The long support rod 3 has sufficient length to absorb the differential expansion between the building steel and the channel 4. Differential expansion between the inverted channel and the roof tubes is absorbed by sliding between the tube support lug 5 and the tube support bar 7. I I 7 When the skin casing is welded in place, it is pressed firmly on the tubes and the tubes at this time should be released from whatever is employed to hold them during erection so that they rest on the bar 7. By placing the tubes in this location before welding the skin casing flange 9 to the inverted'channel 4, the skin casing will form a structural member which resists upward movement of the tubes. The upward forces from the tubes as well as the gas pressure against the skin casing is transmitted into the channel 4 and then through the support rod 3 which has suflicient stiffness to resist the nominal forces which occur due to gas pressure within the passageway.

The embodiment of FIGURES l and 2 is used in areas where there is no other heating surface to be supported in the general area. In steam generators, however, steam superheating surface is frequently suspended in the gas passageway. A support for such heating surface is illustrated in FIGURE 3. The steam superheating tubes '12 which extend downwardly to form the steam superheating surface are supported through a high crown seal which includes inverted U-shaped' channels 13 through which the tubes pass. These channels are extended and welded to fiat roof bars 14 which run transverse to the roof tubes 2. The sealing arrangement which, supports the'sujgierheater elements and is located between the two roof bars 14 is a gas-tight arrangement which is known as a high crown furnace seal. FIGURES 3 and'4 illustratefthe use of my invention in conjunctionwitlisuch a high crown seal. i

The roof bars of the high crown seal are supported by support rods 15 which extend upwardly and are secured to the building steel overhead. These rods are of sufficient strength to carry the weight of the sup'erheaterassemblies as well as the weight of the roof. The weight of the individual roof tubes is thrown into the roof bar 14 through an elongated U-shaped lug 17. The operative portion of this lug insofar as support of thetube is concerned is only the lower leg of the lug. -However, the upper portion of the lug is retained so that it may be welded. to the roof bar 14 at this upper edge thereby forming a welded joint which has a sufficient moment to avoid excessive stresses at'the weld. 1

U-lugs 5 are welded to the roof. tubes 2 in the same manner as described in the previous embodiment. These tubes vare then drawn up so that the upper edge of the tube touches the lower edge .ofthe roof lug 14. The elongated support bar 17 is then slipped through the bar 5 as illustrated and drawn upwardly so that it bears against the upper edge of the lug 5.. While being held in this location this lug is then welded to the roof bar 14.

The skin casing 8 is placed against the roof tubes 2 and bent upwardly around the support arrangement so that it may be welded through flange 19 to the roof bar 14. In this embodiment the skin casing is not operative to hold the roof tubes down, however the roof bar 14 This permits the skin casing 8 to come in inbeing placed in contact with the roof tubes 2 is the memher which resists upward movement of the roof tubes.

While I have illustrated and described a preferred em bodiment of my invention it is to be understood that such is merely illustrative and not restrictive and that variations and modifications. may be made therein without departing from the spirit and scope of the invention. I therefore do not wish to be limited to the precise details set forth but desire to avail myself of such changes as fall within the purview of my invention.

What I claim is:

1. In a fluid heater having a heating gas flow passage and generally horizontal and parallel roof tubes covering the top of the gas passage, an apparatus for supporting said tubes comprising: a U-shaped lug welded on each supported tube with the axis of the center line through the opening of the lug being parallel with the tube and the legs of the U-lug pointing downward; a bar parallel to the supported tube and above the tube extending through the U-lug in sliding contact with the inner edge of the top of the U-lug; a horizontal rigid imperforate support member running transverse the tubes and supporting said bars from the lower edge of said member; and a skin casing of thin metal immediately adjacent the upper surface of said roof tubes and having the edges bent upwardly and welded to said support member above the lower edge of said member, so that said skin casing and support member form a generally gas-tight seal with the bar being supported from said member on the gas flow passage side of the gas-tight seal. 2. In a fluid heater having a heating gas flow path and generally horizontal and parallel roof tubes comprising the top of the gas passage, an apparatus for supporting said tube comprising; a U-lug welded to the upper portion of the supported tubes with the center line through the opening of the lug extending parallel to the tubes; 2. bar located parallel with each of the supported tubes and extending through the U-lug in sliding contact with the inner surface of the top of said U-lug; means for supporting said bars including a member running transverse the tubes and being rigid with respect to re- Straint'of vertical loading; a gas-tight enclosure enclosing within the gas passage side of the heater said bars and U-shaped lugs, said means for supporting said bars forming a portion of said gas-tight enclosure; and means in sliding contact withrthe upper edgeof said tubes rigidly secured to said member running transverse to the tubes for restraining the tubes from upward movement relative to said memberso that the U-lug and bar remain generally in sliding contact despite upward forces which may be exerted on the tubes. 1 I

3. In a fluid heater having aheating gas flow passage and generally horizontal: and parallel. roof tubes for conveying the fiuid being heated, said roof tubes comprising the. roof of the gas passage, an apparatus for supporting said tubes comprising: a U-lug welded to the upper'portion of each of the supported tubes with the center line through the opening of the lug extending parallel to the tube; building steel for supporting the fluid heater; an inverted imperforate channel located directly above said roof tubes and running transversely to said roof tubes; means for supporting said channel from said building steel; skin casing of thin metal adjacent the upper surface of said roof tubes and being bent upwardly at the edges forming a flange with said flange being welded to said channel, whereby said skin casing and said channel form a gas-tight seal; bars secured to the lower flanges of said channel passing through said U-lugs and being in sliding contact with the upper edge of said U-lugs; and said skin casing beingwelded to said channel so that said flange operates to restrain upward movement of said roof tubes relative to said channel.

4. In a fiuid heater having a heating gas flow passage and generally horizontal and parallel root tubes comprising the roof of said gas passage an apparatus for supporting said tubes comprising: a U-lug welded to the upper half of each of the supported tubes with the center line through the opening of the lug extending parallel to the tube; a flat bar extending vertically from said roof tubes and running transverse to said roof tubes located directly above said roof tubes; horizontal support members extending outwardly from said fiat bar with said support members passing through said U-lugs and being in sliding contact with the upper inner surface of said U-lugs; a gas-tight skin casing in contact with the upper surface of said tubes and passing upwardly over said U- lugs and support means and being welded to said fiat bar to enclose said support means and U-lugs within the gas passage side of said gas-tight enclosure.

5. In a steam generator having a heating gas flow passage and generally horizontal and parallel roof tubes forming the top of said gas passage, vertical superheater elements extending into said gas passage and passing between said roof tubes, gas-tight superheater element support structure located directly above said roof tubes and including a pair of laterally spaced, vertically oriented fiat bars extending transverse to said roof tubes with the portion intermediate said spaced fiat bars being a gastight seal, an apparatus for supporting said roof tube comprising: a U-lug welded to the upper half of each of the supported tubes with the center line through the opening of the lug extending parallel to the tubes; horizontal tube support means extending outwardly from one of said fiat bars directly above each of said supported tubes in a direction parallel to the tube, said bar extending through the U-lug and being in sliding contact with the inner surface of the top of said U-lug; means for supporting said superheater element structure; gas-tight enclosure comprising a skin casing of thin metal in contact with the upper edge of said roof tubes and passing upwardly over said tube support means and being welded to said fiat bars so as to include said tube support means within the gas flow passage side of said gas-tight enclosure.

References Cited by the Examiner UNITED STATES PATENTS 2,241,966 5/1941 Smith l22235 2,515,443 7/1950 Ebbetts l22235 2,757,649 8/1956 Coughlin l225l0 X KENNETH W. SPRAGUE, Primary Examiner. 

1. IN A FLUID HEATER HAVING A HEATING GAS FLOW PASSAGE AND GENERALLY HORIZONTAL AND PARALLEL ROOF TUBES COVERING THE TOP OF THE GAS PASSAGE, AN APPARATUS FOR SUPPORTING SAID TUBES COMPRISING: A U-SHAPED LUG WELDED ON EACH SUPPORTED TUBE WITH THE AXIS OF THE CENTER LINE THROUGH THE OPENING OF THE LUG BEING PARALLEL WITH THE TUBE AND THE LEGS OF THE U-LUG POINTING DOWNWARD; A BAR PARALLEL TO THE SUPPORTED TUBE AND ABOVE THE TUBE EXTENDING THROUGH THE U-LUG IN SLIDING CONTACT WITH THE INNER EDGE OF THE TOP OF THE U-LUG; A HORIZONTAL RIGID IMPERFORATE SUPPORT MEMBER RUNNING TRANSVERSE THE TUBES AND SUPPORTING SAID BARS FROM THE LOWER EDGE OF SAID MEMBER; AND A SKIN CASING OF THIN METAL IMMEDIATELY ADJACENT THE UPPER SURFACE OF SAID ROOF TUBES AND HAVING THE EDGES BENT UPWARDLY AND WELDED TO SAID SUPPORT MEMBER ABOVE THE LOWER EDGE OF SAID MEMBER, SO THAT SAID SKIN CASING AND SUPPORT MEMBER FORM A GENERALLY GAS-TIGHT SEAL WITH THE BAR BEING SUPPORTED FROM SAID MEMBER ON THE GAS FLOW PASSAGE SIDE OF THE GAS-TIGHT SEAL. 